This is an important and helpful article, but perhaps the most important part here is a simple observation about the very serious error made by those who are attempting to innovate against the Church’s stable and secure teaching on marriage:
As we have seen, by insisting that a person having contracted a valid canonical marriage can civilly contract a second marriage, rightly so called, with someone else, Schockenhoff explicitly denies premise (2). While for him, one cannot be canonically married to two people, one can be simultaneously married to two people in two different ways: canonically in the one case and civilly in the other.
This is incredibly important because it underlines how misguided it is for those who oppose the regime’s use of force to mandate lies about “marriages” between those fundamentally incapable of marriage (like those already married, whatever papers some bureaucrat may have in a file box, or same-sex couples, or those who have mutilated themselves to become sterile) to proceed by insisting that “marriage” be henceforward bifurcated. As natural marriage is, in fact, marriage, however first attested, it will always be necessary for the Church to account for the public meaning of “marriage,” because there can be no coherent differentiation of the two. Certainly, the Church must tell the regime that is has lied in its paperwork, and must tell all people not to become complicit in this lie–but it cannot do this by permitting a bifurcation of one reality into two putative “marriages” that must, always, in each case, be resolved into one thing, whether reality or delusion.
I tackled this in my responses to the 2015 Survey, especially at some length in response to question 23.